I had the same strange problem, annoying enough that everything worked for quite a while. Then, with some changes, this error occurred. The return code did not help. After a whole day of searching and thinking, I still don't know what caused this, but I know that this is not my code!
My theory is that either my git repository was somehow corrupted, or because I edited my project with a beta version of the IDE + SDK. In any case, you should probably look into re-creating your web view in InterfaceBuilder. Or, re-create your project (or at least partially to confirm that this may be a mistake in the project itself). I think / hope the error disappears then.
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